1. Field of the Invention
The present invention relates to detection of a failure of a clutch mounted on a vehicle.
2. Description of Related Art
Some clutches mounted on vehicles are provided with a drive-side member (for example, a friction disk) that rotates upon receipt of engine torque, and a driven-side member (for example, a clutch disk that is pressed by the drive-side member to rotate together with the drive-side member. The drive-side and driven-side members wear out after long service, which can lower the degree of engagement of the clutch relative to the initial degree. In addition, when hydraulic pressure is used to engage or disengage the clutch, bubbles are formed within a hydraulic hose, which can cause incomplete clutch disengagement.
Conventional vehicles that actuate an actuator to engage or disengage the clutch according to a rider's gear shifting instructions employ technology for detecting and informing the rider of clutch failures. For example, JP-B-Hei 7-56299 provides a device with a potentiometer for detecting the position of a movable part of an actuator that engages or disengages the clutch (hereinafter referred to as clutch position). Based on the detected clutch position, the device determines the presence or absence of a clutch failure. Specifically, the device determines that a failure has occurred if the clutch position at which the driven-side member starts rotating falls outside an appropriate range that is predetermined at manufacturing.
However, when the vehicle runs downslope, the clutch position at which the driven-side member starts rotating is closer to a clutch position at which the clutch is disengaged, compared to when the vehicle runs on a flat road. Meanwhile, when the vehicle runs upslope, the clutch position at which the driven-side member starts rotating is closer to a clutch position at which the clutch is engaged, compared to when the vehicle runs on a flat road. Thus, the gradient of the slope must be considered in predetermining an appropriate range of the clutch position for the device of JP-B-Hei 7-56299. This makes it difficult to predetermine the appropriate range that leads to accurate failure detection.